/*
 * Program to sort integers read from a file and write results to a file:
 *
 * Input and output filenames are given by command-line arguments.
 * Maximum number of integers to allow is given by (compile-time) parameter
 * ARRAY_SIZE.
 */
#include <stdio.h>
#include <stdlib.h> /* has EXIT_SUCCESS, EXIT_FAILURE */

#define ARRAY_SIZE 10000

void sort(int a[], int size);
int find_out_of_order(int a[], int size);

/* main program */
int main(int argc, char* argv[]) {

    if (argc < 3) {
        fprintf(stderr, "usage %s infile outfile\n", argv[0]);
        return EXIT_FAILURE;
    }

    FILE* infile = fopen(argv[1], "r");
    if (infile == NULL) {
        fprintf(stderr, "cannot open input file %s\n", argv[1]);
        return EXIT_FAILURE;
    }

    int data[ARRAY_SIZE];
    int count = 0;
    int temp;
    while (fscanf(infile, "%d", &temp) == 1) {
        if (count < ARRAY_SIZE) {
            data[count++] = temp;
        }
        else {
            fprintf(stderr, "array size %d exceeded\n", ARRAY_SIZE);
            return EXIT_FAILURE;
        }
    }
    if (!feof(infile)) {
        fprintf(stderr, "invalid input at line %d\n", count+1);
        return EXIT_FAILURE;
    }

    fclose(infile);

    FILE* outfile = fopen(argv[2], "w");
    if (outfile == NULL) {
        fprintf(stderr, "cannot open output file %s\n", argv[2]);
        return EXIT_FAILURE;
    }

    sort(data, count);
	int out_of_order = find_out_of_order(data, count);
	if (out_of_order < 0) {
		printf("sorted\n");
	}
	else {
		printf("not sorted\n");
		printf("first out-of-order element at index %d\n", out_of_order);
	}

    for (int i = 0; i < count; ++i) {
        fprintf(outfile, "%d\n", data[i]);
    }
    fclose(outfile);

    return EXIT_SUCCESS;
}

/* 
 * check whether array is sorted:
 * returns index of first out-of-order element, or -1 if all are in order
 */
int find_out_of_order(int a[], int size) {
	for (int i = 0; i < size-1; ++i) {
		if (a[i] > a[i+1]) { 
			return i;
		}
	}
	return -1;
}

/* get index of smallest element of a[start .. size-1] */
int index_of_smallest(int a[], int size, int start) {
    int smallest = start;
    for (int i = start+1; i < size; ++i) {
        if (a[i] < a[smallest])
            smallest = i;
    }
    return smallest;
}

/* sort array (selection sort) */
void sort(int a[], int size) { 
    for (int i = 0; i < size-1; ++i) {
        int k = index_of_smallest(a, size, i);
        if (k != i) {
            int temp = a[k];
            a[k] = a[i];
            a[i] = temp;
        }
    }
}